Terpolymers containing maleic anhydride, vinyl acetate and esters of an alpha, beta unsaturated acid



United States Patent C TERPOLYMERS CONTAINING MALEIC ANHY- DRIDE, VXNYLACETATE AND ESTERS OF AN ALPHA,BETA UNSATURATED ACID Peter J. V. J.Agius and Joan Daphne Bryan, Abingdon, and Thomas A. Garbett, Botley,near Oxford, England, assignors to Esso Research and EngineeringCompany, a corporation of Delaware No Drawing. Original application Aug.11, 1958, Ser. No. 754,153, new Patent No. 3,087,893, dated Apr. 30,1963. Divided and this application Feb. 7, 1963, Ser. No. 266,772

4 Claims. (Cl. 260-785) The present invention relates to oil additivescomprising oil-soluble copolymeric products derived from maleicanhydride and unsaturated esters of carboxylic acids, and also relatesto improved methods of making such polymeric additive compounds.

This application is a division of Serial No. 754,153, entitledCopolymers of Maleic Anhydride and Unsaturated Esters, filed August ll,1958, now US. Patent 3,087,893.

The use of additive compounds for oils to improve the detergentproperties and other properties of such oils is Well-known. Suchadditives when added to lubricating and fuel oils used in internalcombustion engines, inhibit corrosion, cylinder wear, and the formationof carbon and varnish on the working parts. While conventional detergentadditives, particularly metal-containing compounds have provedadvantageous in the past, their excessive use, or use under severeconditions, may result in the formation of high ash residues within theengine with consequent lowering of engine efiicie-ncy. Suchconsiderations also apply to fuel oils which contain additives, such aspour-point depressants.

It has now been discovered that oil-soluble copolymeric oil additiveswhich do not result in ash formation and which donate unusually highdetergent, VI improving and your depressant activities when incorporatedin oil compositions suitable for use in internal combustion engines areobtained by copolymerizing maleic anhydride with an alkyl ester of an11,8 unsaturated dicarboxylic acid, and a copolymerizable alkylene esterof a C -C monocarboxylic acid.

It is preferred that the esters of diand mono-carboxylic-acids used toform the copolymers of the present invention are so chosen that amixture of relatively long and short aliphatic side chains are disposedalong the polymer chain. Thus the relatively long side chains may beprovided by (I -C alkyl ester the 11,13, unsaturated dicarboxylic acid,e.g. esters derived from C C alcohols. Enhanced detergency is providedby using straight chain alcohols rather than branched chain alcohols.The preferred 0a,}? unsaturated dicarboxylic acids are C -C aliphaticacids and preferably fumaric acid, although maleic or itaconic acids maybe used. The relatively short side-chains are preferably provided byusing C C alkylene esters of C -C carboxylic acids, preferably vinyl orallyl esters, and particularly vinyl acetate.

The molar proportions of the monomers preferably used in preparing thecopolymers according to the present invention are:

3,234,186 Patented Feb. 8, 1966 vary between wide limits, e.g. 10,000 to100,000 Standinger, preferably 50,000l00,000.

5% by weight of such copolymers are capable of suspending at least 55wt. percent of sludge in the used oil sludge test, hereinafterdescribed, and raising the V1 by at least 10 units in a parafiinic oilhaving an initial viscosity of 12 cs. at 210 F. and an initial VI of104.

Oil concentrates of the copolymeric materials hereinbefore described maybe incorporated in lubricating or fuel oils in proportions so as to giveeffective and eco nomic concentrations of the copolymeric material.Generally, from 0.5% to 10% by weight of the copolymeric material in thefinal oil, as used in the internal combustion engine, will endow the oilwith the desired properties, although proportions in excess, or lessthan this, may be required, depending on the potency of the particularcopolymer used. Thus for motor lubricants sufiicient additive should beadded so that the final viscosity index of the oil is raised to about 95to 160. The additives of the present invention also have the effect ofincreasing the viscosity of the oil in which they are incorporated. Thefinal oil viscosity should be made to correspond to the requirements ofthe oil, e.g. SAE 10-30 motor oil. Generally about 5 wt. percent of theadditive will be found sulfi-cient to provide these properties.

When the copolymeric materials are incorporated in lubricating oils, itis preferred that mineral lubricating oils be used, although oilsderived from animal or vegetable sources may also be used, as may besynthetic lubricating oils, especially those comprising complex estersof diesters, or mixtures thereof.

The additives may also be incorporated with advantage in fuel oils, suchas diesel oils, gas oils and kerosenes. In such lighter oils, 0.1% to 4%by weight is used.

Oil compositions containing the additives of the present invention mayalso include conventional fuel or lubricating oil additives, such asoil-soluble sulphonates, metal salts of alkyl phenol sulphides, andextreme pressure, anti-wear and anti-oxidant additives.

The copolymers of the present invention may be prepared by anywell-known process, such as low temperature Friedel-Craftspolymerisation, ionic or radiation polymerisation processes.Free-radical-producing catalysts, e.g. peroxide-type catalysts areparticularly useful,

such as benzoyl, acetyl, stearoyl or urea peroxide.

The present invention may be illustrated by the following example.

EXAMPLE 1 The following mixture was polymerized at 60 C. under Thepolymeric product Was stripped under vacuum and 5% by weight wasdissolved in a paraflinic mineral oil having the properties shown, i.e.a viscosity at 210 F. of 12 cs. and a viscosity index of 104. Thesolution was designated Blend A. Preferred g fggl gg The properties ofthis blend are given in Table I.

percent I percent T bl I Maleic anhydride 2-15 10-12 Base oil Blend ".AAlkyl ester of (1,5 unsaturated drcarboxylic acid 25-50 Ila-45 I i 4 OAlkylene ester of C -C monoear- Kinematic viscosity in 0.5. at 100 F-108 145 boxylic acid 40-70 45-55 Kinematic viscosity in as at 210 F 121G Viscosity index- 104 117 Percent vol. dry used oil sludge suspended.3

The molecular weights of the final copolymers may The sludge suspendingability of the oils in the above example was determined by measuring theamount of dry used engine oil sludge that the blend would hold insuspension, using grams of dried used oil sludge and 90 grams of theblend. The blend plus sludge was heated to 200 F. in an oil bath underconstant stirring. The mixture was allowed to settle for 24 hours at 200F., and the top 25 cc. of the mixture was poured into a centrifuge anddiluted with hexane to a total volume of 100 cc. The mixture was thencentrifuged. The percentage weight of solids collected is a measure ofthe detergent powers of the blend.

An important modification of the present invention is concerned with animproved method of preparation of the copolymers of the presentinvention whereby they impart an enhanced viscosity index and detergencyto oil solutions containing them.

It has now been discovered that if a free radical catalyst whichdecomposes at a temperature above 70 C. is used to copolymerize themonomers, an improved copolymeric product is obtained compared with asimilar product obtained using a free radical catalyst decomposing below70 C. such as benzoyl peroxide. The preferred catalyst used in thisimproved process is tertiary butyl perbenzoate. Other catalysts whichmay be used are tertbutyl hydroperoxide, 2,2-bis-(tert-butyl-peroxybutane), di-tertiary-butyl peroxide, di-cumyl peroxide.

It is of course necessary to carry out the copolymerisation at atemperature below the temperature at which degradation of the monomerand copolymer reactants occurs, for example above 200 C. However, thisupper limiting temperature is easily ascertainable by a chemist. Anotherway of defining this improved process is that the copolymeric reactionis carried out at a temperature between 70 and 100 C., using a peroxidecatalyst which does not decompose below 70 C.

The catalyst may be used in the form of an oil solution or slurry, andthe reaction is preferably carried out under an inert gas, e.g.nitrogen, the reactants being agitated, either by stirring or bubblingthe inert gas through the mixture. The reaction is carried out for aperiod of time sufficient to copolymerize the reactants, but not for atime long enough to form an insoluble gel. Thus after several hours ofsteadily increasing viscosity complete polymerisation is indicated by arelatively sudden increase in viscosity. A preferred criterion is tocontinue the reaction until the mixture reaches a viscosity of about 400stokes at the reaction temperature, and then dilute the reaction mixturewith an oil, the copolymer being stripped under vacuum. Theoil-concentrate of the stripped polymer may then be incorporated inoils, e.g. hydrocarbon fuel or lubricating oils as desired.

The catalyst may be used in proportions up to 1% or more based on thetotal reaction mixture.

The beneficial effect obtained by this improved process may beillustrated by the following example.

The monomer mixture was then divided into two parts, part A beingcopolymerised at 60 C. using 1% benzoyl peroxide and part B beingcopolymerised at 90 C. using 0.4% tertiary butyl perbenzoate.Copolymerisation was continued in both instances until a reactionmixture having a viscosity of 400 stokes at the reaction temperature wasobtained. This final viscosity corresponds to substantially completepolymerisation of the reactants, and a relatively sudden increase in therate of thickening of the reactants to this value occurred after severalhours reaction time. The copolymeric products were diluted with an SAE10 type paraffinic oil. The solution was then stripped under a reducedpressure of 5 mm. Hg at 100 C., until the solution contained of theactive polymer.

The copolymer/ oil concentrate obtained by the above procedure was thenadded to a mineral lubricating oil of kinematic viscosity 5.1 cs. at 210F. to produce blends containing 5% of active ingredient.

Table II shows the properties of these blends. The sludge suspendingability of the blends was determined It is to be noted that usingidentical monomeric mixtures, polymerisation at a temperature above 70C. using tert butyl perbenzoate catalyst produced a superior prodnotover that obtained by reaction at C. using benzoyl peroxide catalyst, inthat both the VI and the sludge dispersancy of oils containing it wereenhanced.

What we claim is:

1. An oil-soluble polymer prepared from 2 to 15 mol percent of maleicanhydride, 40 to mol percent of vinyl acetate, and 25 to 50 mol percentof an ester derived from a C to C aliphatic alcohol and an alpha,-beta-unsaturated dicarboxylic acid, said polymer having a Staudingermolecular weight in the range of 10,000 to 100,000.

2. Oil-soluble polymer as defined by claim 1 wherein said ester is a Cto C aliphatic alcohol fumarate.

3. A process for preparing an oil-soluble polymer which comprisescopolymerizing a mixture of from 2 to 15 mol percent of maleicanhydride, 40 to 70 mol percent of vinyl acetate, and 25 to 50 molpercent of an ester derived from a C to C aliphatic alcohol and analpha,beta-unsaturated dicarboxylic acid at a temperature between 70 andC. in the presence of tert. butyl perbenzoate for a time suflicient toform a copolymer having a Staudinger molecular weight in the range of10,000 to 100,000.

4. A process for preparing an oil-soluble polymer which comprisescopolymerizing a mixture of from 2 to 15 mol percent of maleicanhydride, 40 to 70 mol percent of vinyl acetate, and 25 to 50 molpercent of a C to C aliphatic alcohol fumarate in the presence of acatalytic amount of tertiary butyl perbenzoate at a temperature in therange of 70 to 100 C. for a period of time sufficient to achieve akinematic viscosity of about 400 stokes at the reaction temperature.

References Cited by the Examiner UNITED STATES PATENTS 2,810,744 10/1957Popkin 260-785 2,825,717 3/1958 Cashman 26078.5

FOREIGN PATENTS 758,203 10/1956 Great Britain.

JOSEPH L. SCHOFER, Primary Examiner.

DONALD E. CZAIA, LEON I. BERCOVITZ,

Examiners.

1. AN OIL-SOLUBLE POLYMER PREPARED FROM 2 TO 15 MOL PERCENT OF MALEICANHYDRIDE, 40 TO 70 MOL PERCENT OF VINYL ACETATE, AND 25 TO 50 MOLPERCENT OF AN ESTER DERIVED FROM A C8 TO C20 ALIPHATIC ALCOHOL AND ANALPHA,BETA-UNSATURATED DICARBOSYLIC ACID, SAID POLYMER HAVING ASTAUDINGER MOLECULAR WEIGHT IN THE RANGE OF 10000 TO 1000000.